In typical commercial or industrial laundry processes, textile materials such as sheets, towels, wipes, garments, tablecloths, etc. are commonly laundered at elevated temperatures with alkaline detergent materials. Such detergent materials typically contain a source of alkalinity such as an alkali metal hydroxide, alkali metal silicate, alkali metal carbonate or other such base component. When the fabric is treated with an alkaline detergent composition a certain amount of carryover alkalinity may occur. Carryover alkalinity refers to the chemistry that is contained within the fabric (that has not been completely removed) that is available for the next step. For example, when the detergent use solution provides an alkaline environment, it is expected that the detergent use solution will provide a certain amount of carryover alkalinity for a subsequent sour treatment step unless all of the detergent use solution is removed by rinsing.
The residual components of the alkaline detergents remaining in or on the laundered item can result in fabric damage and skin irritation by the wearer of the washed fabric. This is particularly a problem with towels, sheets and garments. Sour materials contain acid components that neutralize alkaline residues on the fabric.
Another ongoing problem in the laundering field is the removal soil and/or oily stains from synthetic fabrics. Synthetic fibers, (fabrics having synthetic fibers incorporated therein or made entirely of synthetic fibers), are hydrophobic and oleophilic. As such the oleophilic characteristics of the fiber permit oil and grime to be readily embedded in the fiber, and the hydrophobic properties of the fiber prevent water from entering the fiber to remove the contaminants from the fiber.
The removal of oily stains, especially on polyester has not been successfully addressed. Several solutions have been proposed using soil release polymers. Soil release polymers are widely known to be effective at aiding the removal of oily soils from synthetic fabrics in a laundry wash process. The polymers work by having both hydrophobic and hydrophilic blocks that allow them to adhere to the polyester surface and make it more hydrophilic. By making the surface more hydrophilic the affinity of oily soils, like dirty motor oil, with polyester is reduced which makes the soil easier to remove. This effect is greater when soil release polymers are used over multiple wash cycles, as the polymers are known to buildup on the fabric.
The main wash step of a typical institutional or industrial laundry cycle has a use solution with both high surfactant and high alkalinity (˜pH 11 or higher). Conversely, the final rinse step wash liquor is less reactive as the pH is near neutral and any surfactant has been rinsed away. Therefore, it is desirable to use a soil release polymer in the final rinse step. Unfortunately this class of polymer is not stable in a liquid sour because they are polyester based and react with the acid or oxidizer.
WO96/24657 discloses high alkalinity detergent composition comprising non-ionic surfactant and a soil release polymer. The composition is in powder form and it is delivered into the main wash of an institutional textile washing process. U.S. Pat. No. 6,200,351 relates to an institutional textile washing process in which a soil release polymer is used in a separate pre-treatment step.
As can be seen, there is a continuing need in the art for the development laundry sour treatments after alkaline washing that remove residual caustic, but also that are environmentally friendly and sustainable.
It is an object of the present invention to provide a solid composition used as a post wash laundering step that includes not only a sour component to treat and remove carryover alkalinity, but also includes a stain removal component to provide a mechanism for further oily stain removal, particularly from polyester or other synthetic fabrics.
Other objects, aspects and advantages of this invention will be apparent to one skilled in the art in view of the following disclosure, the drawings, and the appended claims.